1. Technical Field
The present invention relates to a seat belt retractor and, in particular, relates to an electrically actuatable locking mechanism for locking a seat belt retractor to prevent withdrawal of seat belt webbing.
2. Description of the Prior Art
It is known that during a vehicle collision, a seat belt retractor should be locked as quickly as possible to prevent withdrawal of seat belt webbing. By quickly locking the seat belt retractor, the amount of occupant movement within the vehicle is minimized. The desire to quickly lock the seat belt retractor has lead to the development of electrically actuated locking mechanisms for retractors.
U.S. Pat. No. 4,729,525 discloses one such electrically actuated locking mechanism for a retractor. The retractor disclosed in U.S. Pat. No. 4,729,525 is vehicle sensitive and includes a spindle supported for rotation in belt withdrawal and belt retraction directions. An inertia member is rotatable with the spindle. The spindle is also rotatable relative to the inertia member to actuate the locking mechanism. An electromagnet is energizeable upon vehicle deceleration above a predetermined rate to magnetize a core which moves toward the inertia member. When the core engages the inertia member, rotation of the inertia member is slowed, and rotation of the spindle in the belt withdrawal direction relative to the inertia member results. This relative rotation effects actuation of the locking mechanism of the retractor.
U.S. Pat. No. 3,952,966 discloses a seat belt retractor having a ratchet wheel connected to a rotatable spindle. A pawl is supported for pivotal movement toward and away from the ratchet wheel. When the pawl engages a tooth on the ratchet wheel, rotation of the spindle in the belt withdrawal direction is blocked. A spring biases the pawl toward the ratchet wheel. An electromagnet is energizeable to pivot the pawl away from the ratchet wheel.